The field of this invention relates to electronics and more particularly to a mechanical device to rigidize a printed circuit board and to eliminate and/or minimize the bow and twist introduced to the board during various board manufacturing processes.
Boards upon which are mounted specific electronic circuits and components are used extensively within electronic equipment. As circuits increase in complexity, printed circuit boards have been developed into multi-layered boards wherein each layer, with its associated electrical circuits, are a plane within the board envelope. Insulating layers are interleaved with different interconnected printed conductor patterns.
At the present time, boards are manufactured from a variety of board materials. The most common board material is a composition of glass fabrics or fibers bonded with epoxy resins. Other compositions used are made up by various other material like aramid fibers and polymide or polytetrafluoroethylene resins. It is well-known that all boards tend to warp when subjected to heat, wave soldering for example.
Typical manufacturing procedure requires that the board be impregnated with resin and then cured within an over. Curing temperatures of one hundred seventy degrees centigrade are quite common along with a curing pressure of one thousand five hundred pounds per square inch.
Common usage for printed circuit boards is for the board to be "plugged in" to a particular piece of electronic hardware such as a computer. A particular piece of electronic hardware may have literally hundreds of such boards. Each board has its own "slot" in which the board is to be installed. The space allotted to the particular board conforms closely to the board itself. At times, during the manufacture of the board, the board may assume a warped or slightly non-planar configuration which is the result of the various manufacturing processes. This warping of the board may make it impossible to install such in its particular slot.
In the past, it has been known to install a circuit board stiffener on the board to prevent the board from assuming warped configuration. These stiffeners are installed at selected locations, generally both longitudinal and transversely, to insure that the board will be maintained planar. A typical stiffener comprises an elongated metallic bar which is to be mounted in a fixed relationship onto the upper or bottom surface of the board. Typical installation will sue a conventional fastener such as rivet or soldering to securely fixed in position the stiffener to the board. Generally, the stiffener will be constructed of an electrically conductive material and the stiffener may also function as power distributor or as a common electrical ground for a portion of the circuitry embodied within the board.
The mounting of the stiffener on the board by either installing of fasteners or by soldering is a time consuming and expensive procedure. Previous to the present invention, there has not been known an easy quick way to install a stiffener in conjunction with a printed circuit board.